This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-255463, filed Aug. 25, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to a data processing method and apparatus, and a recording medium for an error-correcting product code favorable for use in the recording and transmission of digital data.
More particularly, the present invention relates to a data processing system using an error-correcting product code which comprises an error-correcting outer parity and an error-correcting inner parity which are effective in the case where information data is recorded on a plurality kinds of recording media particularly having a largely different recording density. Here, particularly, in a method for forming the outer parity, a PO series creation by n sets of data items aggregated by n rows is used. Consequently, even when the error-correcting product code block is recorded on a recording medium in an order of data transmission without carrying out data interleave process; the capability of coping with the defect is largely improved.
In a system in which digital data is recorded on an optical disk by bytes (one byte is equal to eight bits) or digital data is transmitted to a transmission channel, a Reed-Solomon error-correcting product code block is constructed to process data. That is, (Mxc3x97N) bytes of data is arranged in a matrix containing an M rowsxc3x97N columns. Then, PO bytes error-correcting word is added to each column of M bytes information portion. Then, PI bytes of error-correcting words are added to each row of N bytes information portion. Then, (M+Po) rowsxc3x97(N+Pi) columns Reed-Solomon error-correcting product code block is constructed. Then, this Reed-Solomon error-correcting product code block is either recorded on a recording medium or transmitted to a transmission channel. The error-correcting processing portion on the information reproduction side of the recording medium and the receiving side of the transmission channel are capable of correcting random errors and burst errors on the information portion by using the error-correcting words PO and PI.
Such Reed-Solomon error-correcting product code block has a higher data processing efficiency with a decrease in a ratio of a redundant portion (Pixc3x97M+Poxc3x97N+Poxc3x97Pi) of the error-correcting word with respect to the whole word referred to as redundancy ratio, namely (M+Po)xc3x97(N+Pi). On the other hand, the error-correcting capability is also heightened with respect to the random error and the burst error with an increase in the Pi and Po.
Here, it is known that the Reed-Solomon error-correcting code block having small M and N, namely small Pi and Po has a lower correcting capability because of relatively higher probability of error in error correction in the case where the Reed-Solomon error-correcting product code blocks having the same redundancy ratio are compared with each other.
On the contrary, it is known that since Pi and Po can be increased at the same redundancy ratio with an increase in M and N, a high error-correcting capability can be obtained. However, such capability cannot be realized unless the constraint conditions described below are satisfied.
A first constraint condition is that M+Po and M+Pi must be equal to or less than 255 bytes as a code length for constructing the Reed-Solomon error-correcting product code block (in the case where the length of the code is eight bits). Incidentally, Pi described above refers to the PI series error-correcting code length while Po refers to the PO series error-correcting code length.
A second constraint condition is a cost constraint resulting from the scale of the hardware.
By the way, when considered on the basis of the above conditions, optical disk standards such as a DVD-ROM, a DVD-RAM, a DVD-R or the like which are the information recording media in recent years are made public as a standard in which the improved Reed-Solomon error-correcting product code block is adopted. Out of these standards, the DVD-ROM and the DVD-RAM are established as DIS16448 (DVD-ROM having a diameter of 80 mm) and DIS16449 (DVD-ROM having a diameter of 120 mm) and DIS16825 (DVD-RAM).
In this DVD standard, the above idea is adopted with respect to the error-correcting word processing method so that the error-correcting capability is remarkably improved with error-correcting word having a small redundancy ratio as compared with the method used in the conventional optical disks.
The concept on the error-correcting method of the DVD is basically described above, the fundamental problem is to what level the target of the random error-correcting capability and the burst error-correcting capability is to be set. In order to set such level, the recording method of the recording medium and the generation of defects resulting from the handling thereof must be considered.
The recording/reproducing method is determined from the recording/reproducing beam spot size resulting from the recording wavelength and the optical system characteristic in the optical disk system. Here, the recording density constitutes a large factor in the determination of the error-correcting method. In particular, in the determination of the burst error correction capability, the defect length such as scratches or the like generated in the handling of the discs can be determined from experience. With respect to the error-correcting capability, the multiplication of line recording density by the physical defect length constitutes a burst error length of information data with the result that the error correcting capability is required to be raised in the improvement of the recording density.
The recording density can be described as follows with particular reference to the reproduction system.
When, a light source wavelength is denoted by xcex, and a numeric aperture of an object lens is denoted by NA, the recording density stands proportional to (NA/xcex)2. The wavelength adopted in the DVD is 650 nm while NA is 0.6.
In the error-correcting method, a row side inner parity of RS (182, 172, 11) and a column side outer parity of RS (208, 192, 17) are adopted by means of PI (inner parity)=10 bytes and PO (outer parity)=16 respectively with respect to the (Mxc3x97N)=(192xc3x97172) bytes information data block in terms of the Reed-Solomon error-correcting product code (RS is referred to as Reed-Solomon). The block used in this error-correcting method is referred to as the error-correcting product code block.
Here, with respect to the error-correcting product code block, the error is corrected in the PI series at first, and an error mark is attached to a row whose error cannot be corrected. Thereafter, at the time of the error correction on the PO series, the error mark is treated as an error position. When the so-called xe2x80x9cerasure correctionxe2x80x9d method for calculating and extracting only error patterns is used, a maximum of 16 rows of burst errors can be corrected. In the DVD, since the recording density is data bit length=0.267 xcexcm, 0.000267xc3x978xc3x97182xc3x9716=6.2 mm is given. It is possible to say that about 6 mm burst error-correcting capability is given.
However, as a next generation DVD an examination is started on an optical disk having a large capacity resulting from further increase in the density. For the increase in capacity exceeding the DVD, the recording density must be increased. Recently, in order to meet such request, a blue laser diode having a wavelength of 450 nm is made public. When such laser diode is used, it is expected that the recording density can be improved by about 2.6 times in the optical system similar to the DVD or the like. With the improvement in the optical system, four to five times higher density can be realized so that a fine image such as a high definition image such as a Hi-Vision or the like can be recorded for two or more hours on one disc.
In such increase in the density (for example, the line density is about twice as compared with the conventional one), only about 3 mm error-correcting capability can be provided with respect to the burst error when the conventional error-correcting method is introduced.
Furthermore, as described above, the error-correcting word length is 255 bytes at most as long as 1 word=8 bit system processing system is used. Since the PO series is 208 bytes in the DVD standard, the burst error correcting capability is close to the limit in the above error-correcting method so that only little improvement can be expected.
In order to expand the error-correcting word length, the word length may only be lengthened. With respect to the word length, a multiple of eight can be easily used. As a consequence, 1 word=16 bits can be considered. The scale of the error-correcting circuit as hardware is extremely large as compared with the conventional one so that there arises many problems.
In such a case, there is generally available a technique in which the burst error-correcting capability is improved while maintaining the error-correcting code length by adopting a data interleave to scatter the burst error.
However, the data interleave is not adopted even in the DVD standard. The reason goes as follows: in the case where an error is created which exceeds the error-correcting capability in the reproduction processing in the case of an image signal in which information data is compressed, the error data is scattered with the result that a disadvantage of the reproduced image is generated at many positions. In the reproduction processing of the image signal, it is thought that processing of concentrating and reproducing disadvantageous images as much as possible is favorable as a processing of generated disadvantage. This is because the processing can be completed with the reproduction of an instant disadvantageous image.
Besides, a structure close to the current DVD system is favorable for the upper compatibility with respect to the next generation system.
Points Noted by the Inventors of the Present Invention.
Generally, in the error-correcting processing method such as a package medium or the like, the Reed-Solomon product code block method is introduced in many cases. This is because high performance and high efficiency can be expected with this method in the case where defect error data such as defects generated in package medium or the like is detected and corrected.
With respect to the unit of processed data, 1 word=1 byte (8 bits) is favorable. When the application development of the system is considered, it is required to suppress a processing circuit to an appropriate hardware scale. Besides, this fact is required for facilitating a connection to the recording medium and the transmission channel because a front and rear processing circuit is provided in the recording on the recording medium and data transmission to the transmission channel in addition to the error-correcting processing.
Under these circumstances, use of the Reed-Solomon error-correcting product code block used in the current DVD is optimal as an error-correcting method which can corresponds to a large improvement in the recording density of the recording medium under the above surrounding situation.
row side inner parity RS (182, 172, 11)
column side outer parity RS (208, 19217)
Here, the problem is that it is required to settle the improvement of the burst error correcting capability.
In order to heighten the burst error correcting capability, the error may only be scattered in the error detecting and correcting capability in each of the correction code. However, an image and an acoustic signal as information data are subject to compression coding. In a system for recording and reproducing the compression signal, a data structure or error-correcting processing system is desirable which is capable of suppressing information breakdown to a minimal level in the final reproduction of the image and acoustic signal.
In particular, as countermeasures for dealing with the burst error, the number of errors in one error correction block is decreased by scattering the error signal, so that the error-correcting capability can be improved. However, in the case where errors are present in the number exceeding the error-correcting capability, the dispersion of the error signal will result in the expansion of the damage done on the whole data. Consequently, it is difficult to adopt the method using the error data dispersion, namely, the data interleave, which constitutes the basic concept of heightening the burst error-correcting capability.
(1) Therefore, an object of the present invention is to provide a data processing method and apparatus and a reproducing method and apparatus, wherein the creation of an outer parity is devised which directly affects a burst error-correcting capability.
(2) Furthermore, an object of the present invention is to provide a data processing method and apparatus and a reproducing method and apparatus which can largely improve a burst error-correcting capability even in a correction flag redundancy ratio which is the same as the conventional one in an error-correcting method based on byte data.
(3) Furthermore, an object of the present invention is to provide a data processing method and apparatus and a reproducing method and apparatus which are capable of realizing an error-correcting process on a high-density optical disk using a blue laser having a short wavelength up to a physical error-correcting length larger than the conventional one.
(1A)
That is, in the first method of the present invention, one matrix block is such that a plurality of M rowsxc3x97N columns data sectors are aggregated and formed. Furthermore, sub-blocks each having the same number of Y rows is such that one matrix block is divided and formed. Furthermore, Y error-correcting word blocks P0-1 through P0-y are created with respect to the data in the row (vertical) direction of Y sub-blocks. Then, one error-correcting code block (ECC block) is such that Y error-correcting word PO-1 through P0-y are scattered and arranged in bytes at the end of each row. Furthermore, at the end of each row, a configuration is formed such that an error-correcting word PI in the column (horizontal) direction is added at the end of each block.
Then, the present invention provides either a data processing method or apparatus characterized by constructing the ECC block, or the present invention provides a recording medium in which such ECC block is recorded. Furthermore, the present invention provides a method and an apparatus for reproducing the matrix block by processing such ECC block.
Specifically, for example, in the beginning, a main block is constructed which has larger than the maximum byte numbers (=255 bytes) and has twice as many as rows, the block being constructed as a code length in the Reed-Solomon code in which 8 bits=1 bytes are set as data unit.
Then, for example, an even-number row and an odd-number row of the main block are separated to construct two sub-blocks. An outer parity is created for each row separately in each block. The inner parity is created in each of the rows like the prior art.
(2A)
Furthermore, in another method of the present invention, one error-correcting code block (ECC block) is such that Y error-correcting word blocks PO-1 to PO-y are scattered and arranged in bytes at the end row of the data sector. Furthermore, this error-correcting code block has a configuration such that an error-correcting word PI in the column (horizontal) direction is added at the end of each row.
Then, the present invention provides either a data recording method or apparatus characterized by constructing the ECC block, or a recording medium on which such ECC is recorded. Furthermore, the invention provides a method and apparatus for reproducing the matrix block by processing such ECC block.
Specifically, for example, in the beginning, a main block is constructed which has larger than the maximum byte numbers (=255 bytes) and has twice as many as rows, the block being constructed as a code length in the Reed-Solomon code in which 8 bits=1 byte are set as data unit. Then, for example, in a first sub-block comprising an even-row of the former half area of the main block and an odd-row of the latter half area of the main block, and a second sub-block comprising an odd-row of the former half area of the main block and an even-row of the latter half area of the main block an outer parity is separately created for each of the rows. Furthermore, an inner parity of each of the first and the second sub-block is created in each of the rows in the conventional manner.
When a varied error-correcting code block as described above is adopted, the error data is constructed in a scattered manner as seen from the error-correcting system of the outer parity. There is realized a structure in which actual recording and transmission data observes the actual data order so that no error dispersion is generated at the decoding time.
That is, in the error-correcting method using the conventional error-correcting code block, an outer parity and an inner parity are created and odd to A rowsxc3x97B columns data block. However, in the present invention, as the number of rows of the data block, the number of rows is adopted which is larger than the number of rows of the maximum code length which can be subjected to error coding. The error-correcting code series (PO series) in the row (vertical) direction is divided into two sets. As a consequence, it becomes possible to deal with a data block larger than the conventional one as an error-correcting code block. Furthermore, it also becomes possible to not to scatter the data transmission order which is important in dealing with a compressed image signal or the like so that a burst error-correcting capability can be largely improved.
As described above, in the error-correcting word comprising a product code in which, for example, 8 bits=1 byte constitutes a data unit, it is required that the number of rows and the number of columns are selected so that the byte number of the block in which the information data and the error-correcting word are odd becomes 255 bytesxc3x97255 bytes.
However, generally the information data basically takes a sector structure in which the data amount obtained by adding an ID (Identification Data) and a certain amount of control signal are odd to the data having 512 bytes, 1024 bytes, 2048 bytes, 4096 bytes or the like. Thus, a plurality of sets of such sectors constitute an error-correcting block. Furthermore, numeric values such as 8, 16, and 32 suitable for binary processing is favorable as the number of sectors in the error-correcting blocks for taking a good timing with other signal processing. When such condition is added, the number of rows and the number of columns are limited so that the number of rows and the number of columns become about 200. As one of such example, in the structure in which the conventional DVD standard is adopted, 172 bytesxc3x9712 bytes configures one data sector, and 16 sectors are clustered to configure a data block.
Here, 16 bytes outer parity is generated with respect to the data of each column (12xc3x9716=192 bytes) to scatter and add the outer parity to each row (16) by one byte. As a consequence, 16 sector data block is configured which is a set of (12+1) rowsxc3x97172 bytes block (one sector).
Here, furthermore, 10 bytes inner parity is created with respect to (12+1) rowsxc3x97(172+10) rows error-correcting block. 172xc3x9712 bytes one data sector is such that ID, 12 bytes control signal and 4 bytes error sensing code EDC are inserted into the 2048 bytes main data. Consequently, a product code block can be realized which has a very small redundancy ratio and which enable very efficient detection and error.
However, increasing the number of rows in the row (vertical) direction is limited as it is, and it is impossible to improve the error-correcting capability with burst characteristic without raising the redundancy ratio.
Then, according to the present invention, the error-correcting block in the DVD standard is set to two blocks unit. The even-number row and the odd-number row are separated and handled to create an error-creating word PO in each row direction of the even-number row and the odd-number row. As a consequence, the burst error-correcting capability can be improved by two times. The error-correcting block is set to 32 blocks unit. However, the method of the present invention can be used by somewhat correcting the data reading order of the conventional DVD error-correcting method. Furthermore, there is an advantage in that the data processing in the conventional sector unit can be used so that the method can bee linked to the application standard used in the DVD as it is.
The present invention can be described in the following manner in terms of the constituent element.
(1B)
According one embodiment of the present invention, there is provided a data processing method characterized in that:
digital data is processed in bytes to constitute one information data block in (Mxc3x97N) bytes of M rowsxc3x97N columns;
data is arranged in bytes in the information data block, so that data is arranged in the data transmission order from the 0th column to the (Nxe2x88x921)-th column for each row while data is arranged in the data transmission order from the 0th row to the (Mxe2x88x921)-th row;
(Kxc3x97M) rowsxc3x97N columns matrix block is further arranged which is a set of the information data block, and which is constituted of K information data blocks composed of information data blocks from the 0-th information data block to the (Kxe2x88x921)-th information data block which continue in the data transmission order;
on each column of (Kxc3x97M) bytes of the matrix block, an error-correcting word PO-a (Kxc3x97Q) or PO-a ((K/2)xc3x97Q) bytes is created at least with respect to only even-number data (Kxc3x97M/2) bytes, and an error-correcting word PO-b (Kxc3x97Q) or PO-b ((K/2xc3x97Q) bytes is created at least with respect to only odd-number data (Kxc3x97M/2) bytes;
PO-a and PO-b are scattered and arranged into K information data blocks which is constituted of (Mxc3x97N) bytes of M rowsxc3x97N columns;
each column of N columns is formed as (Kxc3x97(M+Q)) or (Kxc3x97(M+2Q)) bytes of Reed-Solomon code PO (Q is an integer of 1 or more); and
the error-correcting word P bytes is further added for each row of N bytes and each row of (Kxc3x97(M+Q)) or (K (M+2Q)) rows is formed as (N+P) bytes Reed-Solomon code PI;
whereby as an overall block, an error-correcting product code block is realized which constitutes (Kxc3x97(M+Q))xc3x97(N+P)) or (Kxc3x97(M+2Q))xc3x97(N+P)) bytes Reed-Solomon error-correcting word having K information data block of (Kxc3x97Mxc3x97N) bytes as information portion.
According to the present invention, an error-correcting code block is constituted wherein the sum of one information data block of (Mxc3x97N) bytes and an average word bytes added to the data block becomes a definite value (M+Q)xc3x97(N+P) or (M+2Q)xc3x97(N+P).
(2B)
According one embodiment of the present invention, there is provided a data processing method comprising:
digital data is processed in bytes to constitute one information data block in (Mxc3x97N) bytes of M rows and N columns;
data is arranged in bytes in the information data block, so that data is arranged in the data transmission order from the 0th column to the (Nxe2x88x921)th column for each row while data is arranged in the data transmission order from the 0th row to the (Mxe2x88x921)th row;
(Kxc3x97M) rowsxc3x97N columns matrix block is further constructed which is a set of the information data block, and which is constituted of K information data blocks composed of information data blocks from the 0th information data block to the (Kxe2x88x921)th information data block which continue in the data transmission order;
on each row of (Kxc3x97M) bytes of the matrix block, an error-correcting word PO-a{(K/2)xc3x97Q bytes} is created with respect to the (k/2)xc3x97(mi+mj) bytes which is constituted by aggregating the even-number rows and the odd-number rows specified in the K information data block order, and an error-correcting word PO-b {(K/2)xc3x97Q bytes} is created with respect to the (K/2)xc3x97(mj+mi) bytes which is constituted by aggregating the remaining even-number rows and the odd-number rows specified in the K information data blocks;
the PO-a and the PO-b are scattered and arranged into the K information data blocks composed of (Mxc3x97N) bytes of M rowsxc3x97N columns;
each column of N columns is formed as two sets of Reed-Solomon code PO of (K/2)xc3x97(mi+mj)+Q) bytes and (K/2)xc3x97(mj+mi)+Q) bytes (however, M=mi (the number of even-number rows)+mj (the number of odd-number rows) and (Q is an integar of 1 or more); and
the error-correcting word of P bytes is further added for each row of N bytes;
whereby as an overall block an error-correcting product code block is realized which constitutes (Kxc3x97(M+Q)xc3x97(N+P)) or (Kxc3x97(M+2Q))xc3x97(N+P)) bytes Reed-Solomon error-correcting word having K information data block of (Kxc3x97Mxc3x97N) bytes as information portion.
As a consequence, two sets of Reed-Solomon codes P on each row in the column direction constitute an error-correcting product code in which rows constituting respective code series are alternately arranged.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.